﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Study01
{
    internal class Program
    {
        static void Main(string[] args)
        {
            // 计算圆的面积
            double r, s;
            Console.WriteLine("请输入圆的半径：");
            r = double.Parse(Console.ReadLine());
            s = 3.14 * r * r;
            Console.WriteLine(s);
            Console.Read();
        }
    }
}
